#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>

int main()
{
    double sum = 0;
    double a = 1;
    double b = 2;
    double c = 0;

    for (int i = 1; i <= 50; i++)
    {
        c = 1 / a - 1 / b;
        a += 2;
        b += 2;
        sum = sum + c;
    }
    printf("%lf", sum);
    return 0;
}
